JPH04118786U - regulated switching power supply - Google Patents

Abstract

(57) [Summary] [Purpose] Preventing increases in output ripple voltage, changes in EMI characteristics, and frequency dependence of output voltage control stability caused by fluctuations in switching frequency to ensure stable and reliable operation. To provide a highly stabilized switching power supply device. [Structure] In a variable switching frequency power supply device, a circuit that detects the switching frequency of this switching power supply, and a frequency comparison circuit that compares the switching frequency detected by this frequency detection circuit with a reference switching frequency and generates an error frequency signal. The present invention is characterized in that it includes an active dummy circuit connected to the rectifying and smoothing circuit and consuming a dummy current in the direction of reducing the error frequency signal output from the frequency comparison circuit.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention is a stabilization system that variably controls the switching frequency to stabilize the output voltage. The present invention relates to switching power supply devices, and particularly to stabilization of switching frequency.

0002

[Conventional technology]

A stabilized switching power supply stabilizes the output voltage to a constant voltage. However, in this case, like a resonant converter or a self-excited converter, the switching frequency There are devices that stabilize the output voltage by variably adjusting the voltage.

0003

[Problem that the idea aims to solve]

However, in variable switching frequency switching power supplies, the switch The following issues arise due to the adjustment of the switching frequency according to the load. As the switching frequency decreases, the output ripple voltage increases and the load side have an unfavorable impact on By changing the switching frequency, EMI (electromagnetic interf erence (radio wave noise interference) characteristics change, making noise countermeasures difficult. As the switching frequency changes, the stability of output voltage control changes, Nonlinearity must be considered in power supply design, which becomes complicated. This invention solves these problems and eliminates the possibility of switching frequency fluctuations. We have developed a stabilizing switch that provides stable and reliable operation by preventing various inconveniences caused by The purpose of this invention is to provide a switching power supply device.

0004

[Means to solve the problem]

The present invention, which achieves these objectives, can be used as a switching power supply when direct current is imprinted. A primary winding that is connected to the This on/off signal is induced into the secondary winding, and flows through this secondary winding. A circuit that rectifies and smoothes switching signals and the voltage output from this rectifier and smoothing circuit. and a predetermined reference voltage to obtain an error signal. A switching control circuit that sends a control signal to the switching element in the direction of decreasing The switching frequency is adjusted according to the load current.

[0005] A circuit that detects the switching frequency of this switching power supply, this frequency Compare the switching frequency detected by the wave number detection circuit and the reference switching frequency A frequency comparison circuit that generates an error frequency signal is connected to the rectification and smoothing circuit. In addition, a dummy voltage is applied in the direction of reducing the error frequency signal output from this frequency comparison circuit. It is characterized by having an active dummy circuit that consumes current.

[0006]

[Effect]

Each component of the present invention operates as follows. Switching power supplies are common switches. This is a variable switching frequency type output voltage stabilized power supply. The frequency detection circuit is switched The switching frequency is determined, and the deviation from the reference switching frequency is determined using a frequency comparison circuit. Ru. Active dummy circuit ensures that the switching frequency matches the reference frequency. Executing dummy current consumption of switching power supply.

[0007]

【Example】

The present invention will be explained below using the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, the DC power supply Vin is used to rectify and smooth a commercial AC power supply to generate DC voltage, or to generate a battery. It is used. The switching power supply 10 is a resonant converter, and is a DC voltage converter. Vin is input and a stabilized output voltage Vout is supplied to the load side. primary winding n1 is connected in parallel with capacitor C1, and through inductance L1. It is connected to switching element Q1. Inductance L1 is an independent single winding, A resonant circuit is formed with the capacitor C1. The secondary winding n2 is a rectifying and smoothing circuit. 12, and is induced by the on-off current flowing through the primary winding n1. The switching current is converted into a DC voltage and becomes an output voltage Vout. Rectification smoothing circuit 12 are diodes D1 and D2 that are in charge of rectification, and a choke that removes high frequency components. It has a coil L2 and a capacitor C2 in charge of smoothing. Error detection circuit 1 4 compares the output voltage Vout of the rectifying and smoothing circuit 12 with a predetermined reference voltage Vref. This is to find the error signal, and here the output voltage Vout is divided by voltage dividing resistors R1 and R2. The error signal is obtained by applying it to the variable shunt regulator RG. Insulation section 16 is a photocoupler that insulates the primary and secondary sides of the transformer, and is used as the error detection circuit 1. 8 is sent to a switching control circuit 18 on the primary side. The switching control circuit 18 outputs an on/off control signal in the direction in which this error signal becomes smaller. is supplied to the switching element Q1.

[0008] Frequency detection circuit 20 detects the switching frequency of switching power supply 10 For example, when a counter is used in a circuit and insulation between the primary and secondary sides is ensured, It is preferable to input a switching signal induced in the secondary winding n2. frequency comparison circuit 30 is the difference between the switching frequency detected by the frequency detection circuit 20 and the reference frequency. It calculates the deviation and sends a control signal in the direction that reduces this deviation, and the frequency/voltage It has a conversion circuit 32 and an error detection circuit 34. The frequency/voltage conversion circuit 32 is Generates a DC voltage corresponding to the switching frequency detected by the frequency detection circuit 20. For example, a digital/analog converter is used. Error detection circuit 34 is the DC voltage obtained by the frequency/voltage conversion circuit 32 and the reference voltage corresponding to the reference frequency. For example, an OP amplifier U1 is used to compare the voltage Vref. Active The dummy circuit 40 is connected to the rectifying and smoothing circuit 12, and here is a variable resistance element. It consists of a transistor Q2 and a resistor R3 that operate as a child. Transistor Q2 is incorrect. The error frequency signal output from the difference detection circuit 34 is input to the base terminal, and this error signal is The value of the dummy current I1 is determined by changing the resistance value in the direction of decreasing .

[0009] The operation of the device configured in this manner will be described next. Figure 2 shows the load current Iout and the current FIG. 3 is a diagram illustrating the relationship between switching frequencies fosc. In the figure, the solid line is the active When operating the dummy circuit 40, the broken line indicates that the active dummy circuit 40 must be installed. This indicates a case where the device is not operating.

0010 Figure 3 shows the output voltage V32 of the frequency/voltage conversion circuit 32 and the switching frequency fosc. This is a genealogy between. Switching frequency fosc detected by frequency detection circuit 20 Accordingly, the frequency/voltage conversion circuit 32 generates a voltage value V32. Error detection times The line 34 is an active dummy circuit so that the voltage value V32 is equal to the reference voltage Vref. Control 40. This means that for the switching power supply 10, the load current Iout and This means that the dummy currents I1 are equal. Iout +I1=const. (1) As a result, the switching frequency fosc of the switching power supply 10 becomes equal to the load current Iout It remains constant regardless of.

[0011]

[Effect of the idea]

As explained above, according to the present invention, the switching frequency fosc is Since it does not depend on out, it has the following practical effects. The dependence of the output ripple voltage on the load current is eliminated, causing malfunction on the system side. In addition to eliminating the risk of becomes easier. Since the generated noise frequency component is constant, noise can be reduced by filters, etc. It becomes easier to reduce Generally speaking, the higher the frequency, the faster the control response for output voltage stabilization control, and the lower the frequency, the faster the control response. This makes stable control difficult over the entire frequency range. However, the switching frequency If it is constant, stabilization control is easy, and it is necessary to have a power supply device with stable operation and high reliability. Easy to design.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating the relationship between load current Iout and switching frequency fosc.

FIG. 3 is a diagram showing the relationship between the output voltage V32 of the frequency/voltage conversion circuit 32 and the switching frequency fosc.

[Explanation of symbols]

10...Switching power supply 20...Frequency detection circuit 30...Frequency comparison circuit 40...Active dummy circuit

Claims (1)

[Scope of utility model registration request] 1. A primary winding to which a direct current is applied, a switching element that turns on and off the current flowing through the primary winding, and a secondary winding to which this turned on and off signal is induced.
A circuit that rectifies and smoothes the switching signal flowing through this secondary winding, an error detection circuit that compares the voltage output from this rectification and smoothing circuit with a predetermined reference voltage to obtain an error signal, and a circuit that detects an error signal when the error signal is small. a switching control circuit that sends a control signal to the switching element in the direction of
A switching power supply that adjusts the switching frequency according to the load current, a circuit that detects the switching frequency of this switching power supply, a comparison between the switching frequency detected by this frequency detection circuit and a reference switching frequency,
A frequency comparison circuit that generates an error frequency signal, and an active dummy circuit connected to the rectification and smoothing circuit that consumes a dummy current in the direction of reducing the error frequency signal output from the frequency comparison circuit. A stabilized switching power supply featuring: